Arduino:
Working with JSON
How to:
To work with JSON in Arduino, the ArduinoJson library is a popular choice due to its ease of use and efficiency. It allows parsing JSON strings, modifying them, and serializing objects back into JSON strings. Here’s how to use it:
Install the ArduinoJson library: Use the Library Manager in the Arduino IDE and install “ArduinoJson”.
Deserialize a JSON string: Here’s how to parse a JSON string and extract values.
#include <ArduinoJson.h>
const char* json = "{\"sensor\":\"gps\",\"time\":1351824120,\"data\":[48.756080,2.302038]}";
void setup() {
Serial.begin(9600);
StaticJsonDocument<200> doc; // Adjust size according to the JSON document
DeserializationError error = deserializeJson(doc, json);
if (error) {
Serial.print(F("deserializeJson() failed: "));
Serial.println(error.f_str());
return;
}
const char* sensor = doc["sensor"]; // "gps"
long time = doc["time"]; // 1351824120
float latitude = doc["data"][0]; // 48.756080
float longitude = doc["data"][1]; // 2.302038
Serial.println(sensor);
Serial.println(time);
Serial.println(latitude, 6);
Serial.println(longitude, 6);
}
void loop() {
// Empty loop
}Sample output:
gps
1351824120
48.756080
2.302038- Serialize to a JSON string: Here’s how to create a JSON string from data.
#include <ArduinoJson.h>
void setup() {
Serial.begin(9600);
StaticJsonDocument<200> doc; // Adjust size according to data
doc["sensor"] = "gps";
doc["time"] = 1351824120;
JsonArray data = doc.createNestedArray("data");
data.add(48.756080);
data.add(2.302038);
serializeJson(doc, Serial);
}
void loop() {
// Empty loop
}Sample output (formatted for readability):
{"sensor":"gps","time":1351824120,"data":[48.756080,2.302038]}Using the ArduinoJson library effectively allows Arduino projects to communicate complex data structures in a human-readable format, facilitating development and integration with web services.